LibC: Stop leaking FILE* from use of getgrnam and getgrgid

Userland/Libraries/LibC/grp.cpp

@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/ScopeGuard.h>
 #include <AK/String.h>
 #include <AK/Vector.h>
 #include <errno.h>
@@ -58,6 +59,7 @@ void endgrent()
 struct group* getgrgid(gid_t gid)
 {
     setgrent();
+    ScopeGuard guard = [] { endgrent(); };
     while (auto* gr = getgrent()) {
         if (gr->gr_gid == gid)
             return gr;
@@ -68,6 +70,7 @@ struct group* getgrgid(gid_t gid)
 struct group* getgrnam(char const* name)
 {
     setgrent();
+    ScopeGuard guard = [] { endgrent(); };
     while (auto* gr = getgrent()) {
         if (!strcmp(gr->gr_name, name))
             return gr;